The use of litter as a sorbent for pet animal urine and other waste liquids has been known for years. Typically, the litter is placed into a container or in an area in which the pet has been trained to use for urinating and defecating. Many prior art litters have been derived from sand, clay, and other minimally sorbent materials. More recently the useful life and sorbency of these litters has been increased by addition of binders and other additives which cause a clump to form from litter soiled by urine and fecal liquids. See e.g., U.S. Pat. Nos. 5,216,980 and 5,176,107. Formation of soiled litter into a clump, in part, minimizes the spread of urine or fecal liquids thus minimizing contamination of the unsoiled litter surrounding the excreted waste liquids. Additionally, clumping reduces the tracking of the soiled litter out of the litter container.
More recently, natural products such as grains, cellulosic products such as sawdust, woodchips or plant hulls have been used as a litter. See eg, U.S. Pat. Nos. 4,206,718; 4,727,824; 4,883,021; 5,109,804; 5,152,250; 5,690,052; 6,014,947. These natural products were developed in an effort to enhance the sorbency of the litter as well as provide a biodegradable litter. Litters with higher sorbency can minimize odors, reduce the amount of litter required and minimize disposal problems of the wetted litter. Although highly sorbent litters have been prepared, many of them tend to swell excessively when contacted with liquids causing problems such as blockage of sewer or septic lines when flushed down a commode.
The present invention is directed to providing a highly sorbent natural product litter with low swelling and suitable clumping characteristics. The invention also provides methods for preparing and using natural product litters with high sorbency, low swelling and suitable clumping characteristics.